New articulated asteroids (Echinodermata, Asteroidea) and ophiuroids (echinodermata, ophiuroidea) from the Late Jurassic (Volgian/Tithonian) of central Spitsbergen

Abstract

The Late Jurassic–Early Cretaceous Slottsmøya Member of the Agardhfjellet Formation in central Spitsbergen has yielded two new species of asteroids and two species of ophiuroids, one of which is described as new. Polarasterias janusensis Rousseau & Gale gen. et sp. nov. is a forcipulatid neoasteroid with elongated arms, small disc and very broad ambulacral grooves with narrow adambulacrals. Savignaster septemtrionalis Rousseau & Gale sp. nov. is a pterasterid with well-developed interradial chevrons. The Spitsbergen specimens are the first described articulated material of Savignaster and reveal the overall arrangement of the ambulacral groove ossicles. Ophiogaleus sp. is an ophiacanthid with relatively long jaws and lateral arm plates, with a coarsely reticulate outer surface. Here again, we report the first articulated skeletons of this genus, providing unprecedented insights into the disc morphology. Ophioculina hoybergia Rousseau & Thuy gen. et sp. nov. is an ophiopyrgid with a well-developed arm comb and tentacle pores reduced to within-plate perforations starting at median arm segments. These new finds are important additions to the asterozoan fossil record with regard to their good degree of articulation and the high latitudinal position of the localities. They significantly add to the set of exhaustively known fossil asterozoan taxa which play a key role in the phylogenetic analysis and reconstruction of evolutionary history.